A thorough understanding and the further improvement of special conducting plastic mixtures for the accurate dosimetry of photons, neutrons, electrons, and pions and combinations of these radiations is sought. Ionization chambers as a basis of precise dosimetry will be studied in all their ramifications including procedures and required ancillary apparatus. Mixtures designed to simulate various biological tissues, air, and other substances are essential for the development of reliable and practical national and international standards of dosimetry. Those physical characteristics of such mixtures which affect the performance of ionization chambers are to be investigated with respect to dependence on the initial preparation and subsequent molding conditions. Perturbing currents induced by various radiations in cables which transport chamber currents to the measuring circuitry are to be determined. Cable specifications are sought which would minimize such perturbations as well as other disturbing effects. A fuller understanding of depth-dose curves for diverse neutron beams is sought with particular emphasis on the role of chamber geometry and the dose defect at the exit face of a phantom.